Move instances of std::function.

Or replace with llvm::function_ref if it's never stored. NFC intended.

llvm-svn: 272513
diff --git a/llvm/lib/Target/AMDGPU/GCNHazardRecognizer.cpp b/llvm/lib/Target/AMDGPU/GCNHazardRecognizer.cpp
index 9ac1920..4b6cc65 100644
--- a/llvm/lib/Target/AMDGPU/GCNHazardRecognizer.cpp
+++ b/llvm/lib/Target/AMDGPU/GCNHazardRecognizer.cpp
@@ -112,8 +112,8 @@
 // Helper Functions
 //===----------------------------------------------------------------------===//
 
-int GCNHazardRecognizer::getWaitStatesSinceDef(unsigned Reg,
-                              std::function<bool(MachineInstr*)> IsHazardDef ) {
+int GCNHazardRecognizer::getWaitStatesSinceDef(
+    unsigned Reg, function_ref<bool(MachineInstr *)> IsHazardDef) {
   const TargetRegisterInfo *TRI =
       MF.getSubtarget<AMDGPUSubtarget>().getRegisterInfo();